1. Field of the Invention
This invention relates to rolling mills producing hot rolled steel products such as rods, bars and the like, and is concerned in particular with an improved system and method for cooling such products at retarded cooling rates.
2. Description of the Prior Art
It is known to form hot rolled steel rod into rings which are deposited on a conveyor and transported through cooling zones where the rod is cooled at controlled rates in order to achieve desired metallurgical properties. Cooling rates may be accelerated through the forced application of a gaseous coolant, typically ambient air, or the cooling rates may be retarded through the use of insulated covers overlying the conveyor. Examples of the foregoing are disclosed in U.S. Pat. No. 3,320,101 (McLean et al.); U.S. Pat. No. 3,930,900 (Wilson); U.S. Pat. No. 3,940,961 (Gilvar) and U.S. Pat. No. 4,468,262 (Kaneda et al.).
One drawback of such installations is that prolonged exposure of the rings to ambient air encourages the development of surface scale, which must then be removed before the product can be subjected to further processing e.g., wire drawing, machining, etc. Also, cooling rates tend to be non-uniform and somewhat difficult to control.
Other attempts at more uniform retarded cooling have included the use of hot water baths and fluidized beds, but these have not proven to be commercially viable.